package com.yand.thinkingInJava.thinkingInJava21.ShareResource;


import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

class CircularSet{
    private int [] array;
    private int len;
    private int index = 0;

    public CircularSet(int size){
        array = new int [size];
        len = size;

        for(int i = 0 ; i < size ; i ++){
            array[i] = -1;
        }
    }

    public synchronized void add(int i){
        array[index] = i;
        index = ++index % len;
    }

    public synchronized boolean contains(int val){
        for(int i = 0 ; i < len; i ++){
            if(array[i] == val){
                return true;
            }
        }

        return false;
    }
}


/**
 * 进一步说明 多个线程调用用同一个方法，需要影响同一个变量的话，这边的方法需要加锁
 *
 * i ++ 不是原子性操作
 */
public class SerialNumberChecker {
    private static final int SIZE  = 10;
    private static CircularSet serials = new CircularSet(1000);
    private static ExecutorService exec = Executors.newCachedThreadPool();



    static class SerialChecker implements Runnable{

        @Override
        public void run() {
            while(true){
                int serial = SerialNumberGenerator.nextSerialNumber();

                if(serials.contains(serial)){
                    System.out.println("Duplicate: "+serial);
                    System.exit(0);
                }

                serials.add(serial);



            }
        }
    }

    public static void main(String [] args) throws InterruptedException {
        for(int i = 0 ; i < SIZE; i ++){
            exec.execute(new SerialChecker());
            if(args.length > 0){
                TimeUnit.SECONDS.sleep(new Integer(args[0]));
                System.out.println("No duplicates detected");
                System.exit(0);
            }
        }
    }






}
